Hi Nick,This is quite a long lasting thread. Like the rest, I've recently bought a 2-motor Dagu 5 rover and I also have the motor shield you seem to be using.Firstly, I have a bit of a problem. Just to test out the Rover, I hooked up the rover to my Arduino Uno just like you have, also neglecting the encoders and I ran your code. When the rover drives, it favours the right rear motor (making it veer to the right). Any ideas on how to remedy this?

Secondly, my rover needs to navigate an obstacle course and hence needs to know approximately where it is. You mentioned above about using the encoders to determine the no. of revolutions of each wheel. Now, I'm what you would call a 'complete novice' when it comes to Arduino and the like and I was wondering how you would go about using the encoders for this purpose. If you had any instructions for me, or could point me in the direction for some help, I would be greatly appreciative. Cheers!

I doubt the motors all have identical performance, so it is quite likely it would veer a bit. You could try to determine what factor to increase/decrease that motor by to compensate.

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You mentioned above about using the encoders to determine the no. of revolutions of each wheel.

I have a snippet (small example program actually) in the section "Reading the rotary encoders". You could incorporate that to find out whether one wheel is moving faster than the other and perhaps use that as a motor compensation.

However this will be thrown out if the track spins, which it tends to a bit, because if one spins a bit as it comes up to speed the number of counts won't reflect which way it is going.

If you are negotiating an obstacle course a proximity sensors might help keep it going straight. For example, sideways mounted IR emitters/detectors could be used to make sure it is in the middle of the current lane. I haven't tried this, it's just a suggestion.

Please post technical questions on the forum, not by personal message. Thanks!

Compensate by adjusting the PWM value of a particular motor? That's a good idea!

What kind of battery would you recommend to power the motor shield? At the moment, whilst I'm getting my bearings I'm just playing around with 6 regular Alkaline AA batteries but what I've heard is that these may provide an unreliable current/ current drops off quite quickly. I looked at LiPo but they seemed quite expensive at JayCar (~$70 for 12V 3600mAh). Is a regular 9V battery ok for supplying power to the Arduino board?

Also, I seem to remember reading somewhere that you can't disconnect the power supply to the Arduino board whilst the power supply to the motor board is still connected. Will this damage my Arduino board?

Yeah, I was just going to use (for now) a 9V smoke alarm battery to power the board and 6 AA batteries for the motor. So I was thinking to engage the Arduino board to cycle through the program I write I'd just slap a swith between the Arduino power supply and the Arduino board. So I would have a flip switch or something similar. Do you think this would suffice?

Hi Nick,I just wanted to run some things past you and get your opinion. So for the power supply of our rover (the motor shield and the arduino uno board) I'm using a 12 V 1300 mAh Sla battery which is run through a voltage regulator and so the output is a steady 9 V. This is then wired into both the Arduino and into the motor shield.

We are only running the two motor dagu 5 rover and hence we have two channels on the 4 channel motor shield unoccupied. We need to run a third dc motor to raise an lower a bridge but the stall current for the dc motor we have is 6.18 A (this is the motor http://www.mabuchi-motor.co.jp/cgi-bin/catalog/e_catalog.cgi?CAT_ID=fk_260sa). The manual for the shield says that a dc motor with stall current greater than 4.5 A should not be used, else we could damage the shield. My question is can we use this motor with the shield ensuring that we read the current pin for that channel and turning the dc motor off when the current exceeds, say 4 A?Or can we somehow just hook it up through the arduino chip, bypassing the shield? Or do we need to get a motor with a lower stall current?